An enigma solved

I thought it would be of interest to record one use to which the decoded German Enigma messages were put (Back in action at Bletchley Park, the black box that broke the Enigma code, September 7). From May 1944 until May 1945, I was the officer in charge of high-frequency direction-finding on the staff of commodore commanding home fleet destroyers at Scapa Flow. The HFDF equipment was fitted to all our destroyers to detect and locate enemy submarines which transmitted sighting reports to Paris before attacking the Russian-bound convoys the destroyers guarded. This could only be done if the frequencies used by the U-boats were known to us - and, thanks to Bletchley Park, they were.

To try to make life difficult for us, the Germans changed wavelengths periodically, so on two occasions I was ordered to report to the Citadel, as it was known, down beneath Admiralty, and was there handed a plain brown envelope by a duty officer. No black briefcase chained to my wrist - that envelope's contents were too secret. To underline the security which surrounded Bletchley Park, I had no knowledge of its existence - just as Mrs Bourne, the young Wren decoder, had no idea of HFDF and its need for a fraction of the Park's output. Lloyd Stainer Fakenham, Norfolk